1. Field of the Invention
Embodiments of the invention generally relate to a gas distribution plate assembly and method for manufacturing the same in a processing chamber.
2. Description of the Background Art
Photovoltaic (PV) devices or solar cells are devices which convert sunlight into direct current (DC) electrical power. PV or solar cells typically have one or more p-i-n junctions. Each junction comprises two different regions within a semiconductor material where one side is denoted as the p-type region and the other as the n-type region. When the p-i-n junction of the PV cell is exposed to sunlight (consisting of energy from photons), the sunlight is directly converted to electricity through a PV effect. PV solar cells generate a specific amount of electric power and cells are tiled into modules sized to deliver the desired amount of system power. PV modules are created by connecting a number of PV solar cells and are then joined into panels with specific frames and connectors.
PV solar cells typically include a photoelectric conversion unit formed on a large transparent substrate. The photoelectric conversion unit includes a p-type, an intrinsic type (i-type), and a n-type silicon layer sequentially disposed on the transparent substrate. The silicon films that may be utilized to form the photoelectric conversion unit may include polysilicon (poly-silicon), microcrystalline silicon (μc-Si), and amorphous silicon (a-Si) films. Plasma enhanced chemical vapor deposition (PECVD) is generally employed to deposit the silicon films on the transparent substrate. PECVD process is performed by introducing a precursor gas or gas mixture into a vacuum chamber that includes the transparent substrate. The precursor gas or gas mixture is supplied from a distribution plate toward the surface of the transparent substrate. A RF power is applied to the distribution plate and/or a substrate support assembly disposed in the chamber to form a plasma within the precursor gas or gas mixture, thereby depositing a silicon layer with desired film property on a surface of the transparent.
As the demand for larger solar cell substrates continues to grow, maintaining a uniform plasma and/or process gas flow during a PECVD process over the large substrate surface has become increasingly difficult. Film property variation between center and edge portions of films deposited on the large substrates caused by the process non-uniformity present a significant challenge for producing large and efficient solar cells. With ever increasing substrate size, edge to center property variation has become more problematic.
Therefore, there is a need for an improved apparatus for depositing a film having uniform distribution of film properties on large area substrates by a chemical vapor deposition process.